In general, a compressor is a mechanical apparatus for compressing the air, refrigerant or other various operation gases and raising a pressure thereof, by receiving power from a power generation apparatus such as an electric motor or turbine. The compressor has been widely used for an electric home appliance such as a refrigerator and an air conditioner, or in the whole industry.
The compressors are roughly classified into a reciprocating compressor in which a compression space for sucking or discharging an operation gas is formed between a piston and a cylinder, and the piston is linearly reciprocated inside the cylinder, for compressing a refrigerant, a rotary compressor in which a compression space for sucking or discharging an operation gas is formed between an eccentrically-rotated roller and a cylinder, and the roller is eccentrically rotated along the inner wall of the cylinder, for compressing a refrigerant, and a scroll compressor in which a compression space for sucking or discharging an operation gas is formed between an orbiting scroll and a fixed scroll, and the orbiting scroll is rotated along the fixed scroll, for compressing a refrigerant.
Recently, a linear compressor which can improve compression efficiency and simplify the whole structure without a mechanical loss resulting from motion conversion by connecting a piston directly to a linearly-reciprocated driving motor has been popularly developed among the reciprocating compressors.
Normally, in the linear compressor, a piston is linearly reciprocated in a cylinder by a linear motor inside a hermetic shell, for sucking, compressing and discharging a refrigerant. The linear motor includes a permanent magnet disposed between an inner stator and an outer stator, and the permanent magnet is linearly reciprocated due to a mutual electromagnetic force. As the permanent magnet is driven in a state where it is coupled to the piston, the piston is reciprocated linearly inside the cylinder to suck, compress, and discharge the refrigerant.
FIG. 1 is a view illustrating a conventional linear compressor. FIG. 2 is a side cross sectional view enlargedly illustrating a portion A of FIG. 1. FIG. 3 is a graph illustrating the amount transverse displacement of a rear spring in accordance with the amount of compression in the conventional linear compressor.
Referring to FIG. 1, in the conventional linear compressor 1, a piston 30 is linearly reciprocated inside a cylinder 20 by a linear motor 40 in a hermetic shell 10 so as to suck, compress and discharge refrigerant. The linear motor 40 includes an inner stator 42, an outer stator 44, and a permanent magnet 46. The permanent magnet 46 is linearly reciprocated between the inner stator 42 and the outer stator 44 due to a mutual electromagnetic force. As the permanent magnet 46 is driven in a state where it is coupled to the piston 30, the piston 30 is linearly reciprocated inside the cylinder 20 to suck, compress and discharge refrigerant.
The linear compressor 1 further includes a frame 52, a stator cover 54, and a back cover 56. The linear compressor may have a configuration in which the cylinder 20 is fixed by the frame 52, or a configuration in which the cylinder 20 and the frame 52 are integrally formed. At the front of the cylinder 20, a discharge valve 62 is elastically supported by an elastic member, and selectively opened and closed according to the pressure of the refrigerant inside the cylinder. A discharge cap 64 and a discharge muffler 66 are installed at the front of the discharge valve 62, and the discharge cap 64 and the discharge muffler 66 are fixed to the frame 52. One end of the inner stator 42 or outer stator 44 as well is supported by the frame 52, and an O-ring or the like of the inner stator 42 is supported by a separate member or a projection formed on the cylinder 20, and the other end of the outer stator 44 is supported by the stator cover 54. The back cover 56 is installed on the stator cover 54, and a suction muffler 70 is positioned between the back cover 56 and the stator cover 54.
Further, a supporter piston 32 is coupled to the rear of the piston 30. Main springs 80 whose natural frequency is adjusted are installed at the supporter piston 32 so that the piston 30 can be resonantly moved. The main springs 80 are divided into front springs 82 whose both ends are supported by the supporter piston 32 and the stator cover 54 and rear springs 84 whose both ends are supported by the supporter piston 32 and the back cover 56. Here, the main springs 80 include four front springs 82 and four rear springs 84. Accordingly, this large number of the main springs 80 leads to a large number of positional parameters to be controlled in order to maintain balance upon movement of the piston 30. Consequently, the manufacturing process becomes complicated and longer and the manufacturing cost is high.
Referring to FIG. 2 enlargedly illustrating a portion A of FIG. 1, members for supporting the rear spring 84 inside the back cover 56 in the conventional art can be understood in detail. A support portion 58 of the supporter piston 32 and a support portion 59 of the back cover 56 assists the rear spring 84 for resonant movement of the piston 30 while supporting both ends of the rear spring 84.
Referring to FIG. 3, the amount transverse displacement of the rear spring in accordance with the amount of compression in the conventional linear compressor can be understood.
First, with regard to the generation of an amount of transverse displacement upon compression of the rear spring 84 shown in the upper part of the graph, the rear spring 84 is compressed and expanded to repeat resonant movement by being supported by the supporter piston 32 and the back cover 56. Now, a case will be assumed in which the amount transverse displacement of the rear spring 84 is large because of the compression of the rear spring 84. By measurement of the movement of the rear spring 84, a measured value can be shown by a graph wherein the amount of compression and the amount of transverse displacement are an X-axis and a Y-axis, respectively.
In other words, if the rear spring 84 is compressed and moved at δmin to δmax, a measured value having a amount of transverse displacement of Ymin to Ymax of the rear spring 84 is shown by a graph in which the amount of transverse displacement is the smallest when the amount of compression is the smallest and the largest, and the amount of transverse displacement is the largest when the amount of compression is intermediate.
Here, as an amount of transverse displacement is generated at the rear springs 84, this causes an unnecessary contact inside the back cover, produces impurities caused by damage and abrasion of the rear springs, and generates noise.
FIG. 4 is a side view schematically illustrating a case where a gap between the rear spring and the back cover support portion is made larger in the conventional art.
Referring to FIG. 4, it can be seen that when a gap between the lower end of the rear spring 84 and the back cover support portion 59 is made larger, there is no gap formed between the upper end of the rear spring 84 and the support portion 58. Compared with FIG. 3, it is adjusted so as to avoid contact by forming a gap between the support portion 59 of the back cover and rear spring 84. However, axial eccentricity is generated at the upper end portion and the lower end portion due to a manufacturing tolerance caused upon manufacturing of the rear springs 84. As shown in FIG. 4, this gives rise to abrasion of the upper end portions of the rear springs 84 and the support portion 58 of the supporter piston, thereby generating impurities and causing noise.
FIG. 5 is a side view schematically illustrating the shape of a real object in accordance with an eccentricity (e) generated from the rear spring in the conventional art.
Referring to FIG. 5, it can be understood that there exists an axial eccentricity at the upper end portion and lower end portion due to a manufacturing tolerance upon manufacturing of the rear springs 84. Due to the eccentricity, when the rear spring 84 receives an external force, as shown in FIG. 4, abrasion takes place at the upper end portion of the rear spring 84 and the support portion 58 of the supporter piston. Of course, the lower end portion of the rear spring 84 also may undergo unnecessary abrasion at the back cover 56.
As such, in FIGS. 2 to 4, an amount of transverse displacement generated upon compression and expansion of the rear spring 84 and an axial eccentricity of the rear spring give rise to unnecessary contact inside the back cover, produce impurities caused by damage and abrasion of the rear springs, and generate noise.
As described above, since the conventional linear compressor includes four front springs and four rear springs at longitudinally and laterally symmetrical positions, this requires a large number of main springs and a large number of positional parameters to be controlled in order to maintain balance upon movement of the piston. Consequently, the manufacturing process becomes complicated and longer and the manufacturing cost is high.
In addition, when the rear springs are compressed and expanded, an amount of transverse displacement is generated, thereby leading to an interference at the skirt portion of the back cover, generating impurities due to the abrasion and damage of the rear springs, and causing a noise problem.
FIG. 6 is a side cross sectional view schematically illustrating a conventional linear compressor. FIG. 7 is a side cross sectional view enlargedly illustrating a front main spring part of FIG. 6.
Referring to FIG. 6, in the conventional linear compressor 1, a piston 30 is linearly reciprocated inside a cylinder 20 by a linear motor 40 in a heimetic shell 10 so as to suck, compress and discharge refrigerant. The linear motor 40 includes an inner stator 42, an outer stator 44, and a permanent magnet 46. The permanent magnet 46 is linearly reciprocated between the inner stator 42 and the outer stator 44 due to a mutual electromagnetic force. As the permanent magnet 46 is driven in a state where it is coupled to the piston 30, the piston 30 is linearly reciprocated inside the cylinder 20 to suck, compress and discharge refrigerant.
The linear compressor 1 further includes a frame 52 and a back cover 56. The linear compressor may have a configuration in which the cylinder 20 is fixed by the frame 52, or a configuration in which the cylinder 20 and the frame 52 are integrally formed. At the front of the cylinder 20, a discharge valve 62 is elastically supported by an elastic member, and selectively opened and closed according to the pressure of the refrigerant inside the cylinder. A discharge cap 64 and a discharge muffler 66 are installed at the front of the discharge valve 62, and the discharge cap 64 and the discharge muffler 66 are fixed to the frame 52.
One end of the inner stator 42 or outer stator 44 as well is supported by the frame 52, and the back cover 56 is supported by the outer stator 44.
A piston flange 33 projected at one end of the piston 30 in a radial direction is elastically supported in the movement direction of the piston 30 by the front springs 82 and rear springs 84 whose natural frequency is adjusted so that the piston 30 can perform resonant movement.
Here, there is formed a simple structure having one front spring 82 and one rear spring 84 respectively mounted therein. Such a structure of main springs can be referred to as an 1+1 structure.
Referring to FIG. 7, the front springs 82 mounted at the outer side of the cylinder 20 and the inner side of the inner stator 42 supported by the frame 52 form a structure which the piston 30 penetrates.
Here, the cylinder 20 having the front springs 82 mounted at the outer side is difficult to change the dimension of the inner diameter φD. This puts some limitation in designing the cylinder 20, thereby making it difficult to develop a model of a linear compressor.
FIG. 8 is a side cross sectional view schematically illustrating another structure of the conventional linear compressor. FIG. 9 is a perspective view illustrating a main spring assembly of FIG. 8.
In FIG. 8, in the linear compressor 1, a piston 30 is linearly reciprocated inside a cylinder 20 by a linear motor 40 in a hermetic shell 10 so as to suck, compress and discharge refrigerant. The linear motor 40 includes an inner stator 42, an outer stator 44, and a permanent magnet 46. The permanent magnet 46 is linearly reciprocated between the inner stator 42 and the outer stator 44 due to a mutual electromagnetic force. As the permanent magnet 46 is driven in a state where it is coupled to the piston 30, the piston 30 is linearly reciprocated inside the cylinder 20 to suck, compress and discharge refrigerant.
The linear compressor may have a configuration in which the cylinder 20 is fixed by the frame 52, or a configuration in which the cylinder 20 and the frame 52 are integrally formed. At the front of the cylinder 20, a discharge valve 62 is elastically supported by an elastic member, and selectively opened and closed according to the pressure of the refrigerant inside the cylinder. A discharge cap 64 and a discharge muffler 66 are installed at the front of the discharge valve 62, and the discharge cap 64 and the discharge muffler 66 are fixed to the frame 52. A main spring assembly 33 is supported between one ends of the front springs 82 and rear springs 84, and a back cover 56 is supported on the other ends of the rear springs 84. The main spring assembly 33 may have a structure integrated and fixed by a first spring supporter and a second spring supporter. A structure in which four front main springs and four rear main springs are respectively arranged on outer side portions is foimed. The back muffler 75 is connected to the flange of the piston 30. As a suction muffler (not shown) is provided at an inner side of the back muffler 75, it may also be formed at an inner side of the piston 30.
In FIG. 9, the main spring assembly 33 includes a first spring supporter 32a and a second spring supporter 32b connected to the piston 30 so as to move integrally with the piston, front springs 82 mounted between the first spring supporter 32a and a stator cover (not shown), and rear springs 84 mounted between the second spring supporter 32b and a back cover (not shown). As four front springs 82 and four rear springs 84 are alternately arranged, a total of eight main springs are arranged.
As shown in FIGS. 7 and 8, there is provided a structure in which four main springs respectively at the front and rear are mounted at outer side portions, thus enabling a change in the inner diameter of the cylinder 20. As a result, this will be useful in developing various models. Such a structure for main springs can be referred to as a 4+4 structure.
As described above, in the conventional linear compressor, if one front spring and one rear spring are mounted, it is difficult to change the dimension of the inner diameter of the cylinder, thereby making it difficult to develop a model.
Additionally, if four main springs are mounted at the front and rear, respectively, production costs increase, and any problem making it difficult to manufacture and manage the linear compressor occurs.
Moreover, there is a large number of positional parameters to be controlled in order to maintain balance upon movement of the piston. Consequently, the manufacturing process becomes complicated and longer and the manufacturing cost is high.